我国西北地区冬季平均气温的气候特征

Climatic Features of the Mean Temperature in Northwest China during Winter Time

本文对我国西北五省（区）１３５个测站、１９６０－１９９０（代表站１９５１—１９９０）年冬季（１２－２月）平均气温资料用主成分分析等方法就西北区冬季气温的变化进行了分析研究。结果表明：西北地区冬季平均气温变化在空间上具有很好的一致性，但也存在由于地理位置、地形、冷空气入侵路径等的不同而引起气温变化在空间分布上的差异。分析认为，３０－４０年来西北地区冬季气温总趋势是在波动中逐渐变暖的。６０年代最低，７０年代较６０年代升高０．４℃，８０年代较７０年代升高０．６℃，较６０年代升高１．０℃，冬暖趋势明显。青藏高原及个别高山站冬季气温变化趋势与上述情况有所不同，特别是８０年代气温下降明显，表现为冬冷。西北区冬季气温年际变化具有８年周期。

The variations in the winter mean air temperature in Northwest China are studied by main component analysis using the data from 135 observational stations in five provinces or autonomous regions of Northwest China for the period of 1960-1990 (1951-1990 for the representative stations). Results show that the mean temperature variations are spatially well consistent in winter. However, variation in geographic locations, topographic features and courses of cold air invasion may cause difference in the spatial distributions of temperature variation. Analysis indicates that the general trend of the winter temperature change in Northwest China has been a gradual warming with fluctuations for the last 30-40 years. In the 1960s, the winter temperature was quite low. There are increases of 0.4℃ and 0.6℃in the 1970s and 1980s, respectively as compared with that in the previous years. The total increase was 1.0℃. It is obvious that Northwest China has been becoming warmer considerably in the winter months. In contrast, the Qinghai-Tibet Plateau and very few mountain stations have experienced a different trend, especially in the 1980s, when the air temperature dropped enormously and a cold winter was observed. Besides, the annual variation of the winter temperature in Northwest China had a quasi-eight year periodic oscillation.